(a) Field of the Invention
The present inventive concept relates to a film bulk acoustic resonator, a semiconductor apparatus comprising of such an acoustic resonator, and the manufacturing methods thereof.
(b) Description of the Related Art
Thin-film Bulk Acoustic Resonator (FBAR) is a micro-electro-mechanical (MEMS) based radio frequency (RF) device that has been widely used in wireless devices such as cell phone. FBAR device offers high signal sensitivity, wide frequency response spectrum, and good output linearity. It also has a small footprint and can be integrated into existing complementary metal-oxide-semiconductor (CMOS) fabrication processes.
FIG. 1 depicts an example of a conventional FBAR. In manufacturing the structure of FIG. 1, a cavity 101 is first formed in a substrate 100, then the cavity 101 is filled with a sacrificial material (not shown). Then a lower electrode layer 102, an acoustic resonator film 103, and an upper electrode layer 104 are formed, respectively, on the substrate 100 and the sacrificial material. The acoustic resonator film 103 may comprise a piezoelectric film, one or more adhesive layer, and one or more dielectric layer. In order to remove the sacrificial material now buried underneath the lower electrode layer 102, a hole 105 has to be made to penetrate the upper electrode layer 104, the acoustic resonance film 103, and the lower electrode layer 102, respectively, to reach the sacrificial material. The sacrificial material then can be removed by a wet etching process through the hole 105. The hole 105 has some undesirable effects in that it weakens the integrity of the lower electrode layer 102, the acoustic resonance film 103, and the upper electrode layer 104, adversely affecting the performance of the FBAR. Therefore a new acoustic resonator design that eliminates the need for the hole 105 is desired.